Well if you really HAVE to have a Perl Certifcation that is from someone that an Employers HR Dept. MIGHT respect, you could try the one from CIW. It used to be just a test of Perl that was part of another Certification, but now it is a Certification on its own, CIW Perl Specialist.
Sure, a Perl test on a PHP page: that seems legit. ;-)
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James
The HR types love certifications, and the CIW Web Development Professional combination of a front-end scripting language certification, a back-end programming language certification, a database certification, and a web development certification is an easy way for them to check off the boxes for a position in Web Programming and Development.